drivers: can: mark the CAN API as unstable

Mark the Controller Area Network (CAN) driver API as unstable. The CAN
API was introduced in Zephyr v1.14 and has since gained support for many
different hardware platforms.

Signed-off-by: Henrik Brix Andersen <[email protected]>

Author: henrikbrixandersen

doc/reference/api/overview.rst

@@ -48,7 +48,7 @@ current :ref:`stability level <api_lifecycle>`.
      - 2.4
 
    * - :ref:`can_api`
-     - Experimental
+     - Unstable
      - 1.14
      - 2.6